With some exceptions, when the vast majority of the public thinks "Disney vacation" they think "theme park". Disney has a hard time justifying DVC prices at anywhere except near a theme park.
Hilton Head and Vero Beach are both small timeshares compared to the typical WDW DVC resort. Both opened ahead of nearly all WDW DVC resorts at a time when the Disney brand was at its zenith and DVC options were extremely limited. 20 years later, direct and resale prices at those resorts languish far behind prices at WDW DVCs.
Aulani is proof that the public doesn't have an appetite for a Disney timeshare away from a theme park. Opened six years ago, it still hasn't sold out, selling slower than the expansive, beautiful Animal Kingdom Villas, which the public was slow to embrace because of its incorrectly perceived "bad" location on the southwest corner of WDW property. (I still can't figure out why AKV resale prices are about the same as the massive, rather ho-hum SSR. Seriously, AKV is WDW's most beautiful resort.)
Remember, building/converting at WDW is cheap. Disney already owns all the land and infrastructure. Building anywhere else is significantly more expensive for Disney.
This is all about volume and margin. Disney is never going to find a timeshare location that will sell as quickly and with as high of a margin as at WDW.